1. Field of the Invention
The present invention relates a starter having a pinion movement control structure.
2. Description of Related Art
Small-sized and lightweight starters are proposed in Japanese Patent Application Laid-Open No. 8-93607 and No. 50-5807. The starter has a starting motor, an output shaft driven by the starting motor, a pinion spline-fitted on the output shaft, and a pinion rotation restricting member which restricts the rotation of pinion to advance the pinion axially on the output shaft through the helical spline fitting by a rotation difference relative to the output shaft.
In this type of starter, it often occurs that even when the pinion reaches the end side of the ring gear of an engine, the pinion fails to mesh with the ring gear for one reason or another. This may occur when the starter is restarted while the pinion is still in the course of inertia rotation which exists immediately after starting the starter. At this time, the pinion rotation restricting member is still engaged with the pinion and is pulled toward the pinion rotation direction. Thus, the pinion rotation restricting member is subjected to extreme deformation and may possibly break.
Further, while the pinion is moving on the output shaft toward the ring gear, the starting motor picks up rotation speed rapidly thereby causing a large impact upon meshing of the pinion with the ring gear. Therefore, sufficient rigidity to withstand impact is required for a rotational force transmission part of the starter including the pinion.